The present application relates to hand tools, particularly drivers, such as screwdrivers, nut drivers and the like. The application relates in particular to methods of making tool handles.
It is known to provide hand tools with plastic handles which are typically formed of a single plastic material molded around an end of a tool shank.
It is also known to provide tool handles with a two-part construction, including an inner portion formed of a hard or rigid material for the necessary handle strength, and an outer gripping portion formed of a softer and/or more resilient or flexible material for user comfort and to afford a n improved grip by increasing the frictional gripping force between the tool handle and the user""s hand. However, heretofore such dual-material handles have either had a relatively complex and expensive construction or have suffered from slippage of the outer hand grip portion relative to the inner body portion.
Also, in molding prior dual-material handles, it has been difficult to maintain uniform depth of the outer gripping material. Typically, the inner rigid core is supported by its ends as a preform in a mold cavity and the outer resilient or flexible gripping material is injected along one side of the longitudinal extent of the handle and then flows circumferentially around the handle in both directions along substantially the entire longitudinal extent. This can introduce bending or uneven forces on the preform, which can cause uneven depth of material. Also, in the event that there are raised indicia on the preform around which the softer material is to be flowed, these bending forces can result in an improper seal between the tops of the raised indicia and the mold, causing the inflowing material to cover and obscure the indicia. Also, this technique tends to result in a cold knit line in the finished handle extending longitudinally of the preform along the side thereof opposite from the mold inlet gate.
This application describes a technique for providing an improved hand tool with a handle construction which avoids the disadvantages of prior tools while affording additional structural and operating advantages.
The application describes a hand tool with a dual-material handle of simple and economical construction, with a hard core and softer outer grip portion. The handle affords improved user grip and comfort while providing superior bonding of the handle materials and prevention of slippage of the outer grip portion.
An improved method of molding the handle is also disclosed which results in balanced forces on mold preform inserts, good sealing around raised indicia on the preform and avoidance of cold knit lines on the finished handle.
In particular, there is provided a method of forming a hand tool comprising the steps of: injection molding a relatively hard and rigid inner body having an elongated central portion and two end flanges extending laterally outwardly of the central portion around the entire periphery thereof, the central portion having a peripheral groove formed therein adjacent to an end flange, and injection molding around the inner body an outer gripping body formed of a relatively soft and resilient material so as to surround the central portion of the inner body and fill the groove.